Psychiatry
Males have paranoid thoughts, females hallucinations
By HImanshu, UK Correspondent
Oct 6, 2004, 16:14

A new study has found that over one in 20 people in the general population reported experiencing psychotic symptoms.

Being male was associated with paranoid thoughts, whereas female gender predicted hallucinatory experiences.

Factors associated with psychotic symptoms were drug and alcohol dependence, victimisation, recent stressful life events, lower intellectual ability and neurotic symptoms. In terms of drug dependence, the relationship between cannabis dependence and psychotic symptoms was the strongest.

Psychosis is generally thought of as an all-or-nothing phenomenon - you either have it or you do not. However, there is increasing evidence that psychosis exists in the population as a continuum rather than a categorical diagnosis. That is most people who report one or more psychotic symptoms are not clinically mentally ill.

This study, published in the October issue of the British Journal of Psychiatry, used information from the second British National Survey of Psychiatric Morbidity, carried out in 2000. A total of 8580 people aged 16-74 were interviewed. Those who scored positive for one or more psychotic symptoms had a second interview with a clinician. Only one in 250 adults were found by the clinician to be mentally ill with a psychotic disorder such as schizophrenia or manic depressive psychosis.

Questions assessed mental health, physical health, substance use, life events and socio-demographic variables. The Psychosis Screening Questionnaire (PSQ) covered five areas: mania; the feeling that one's thoughts were being interfered with or controlled; paranoia; strange experiences; and hallucinations.

The PSQ consisted of an initial probe question measuring less marked psychotic experiences, and a secondary question relating to more serious psychotic experiences.

So, for example, for paranoia, 9.1% endorsed the question 'Have there been times when you felt that people were deliberately acting to harm you or your interests?' whereas only 1.5% endorsed 'Have there been times when you felt that a group of people were plotting to cause you serious harm or injury?'

It was found that 5.5% of those questioned had experienced one or more of the five psychotic symptoms measured, including the secondary questions for the item (i.e. the 'more psychotic' experiences). This finding is consistent with the existence of a continuum of psychotic experiences in the general population.

The reported figure of 5.5% is lower than the rates of psychotic symptoms found in other studies, possibly because this study measured only five psychotic symptoms through the PSQ, whereas other studies have measured as many as 17, which would be likely to give rise to a higher prevalence rates. In addition, some studies measured lifetime prevalence of psychotic symptoms, whilst this study looked at annual prevalence.

The authors comment that the psychological factors associated with psychotic symptoms in the general population are consistent with psychological models of psychotic symptoms in patients with psychosis.

Neurotic symptoms may contribute to the development of psychotic symptoms, and offer a target for intervention in people with early warning signs of psychosis.

Cannabis dependence may increase the risk of experiencing psychotic symptoms.

Further research is planned using the interview data from both phases of the study.

Reference:
Johns LC, Cannon M, Singleton N, Murray RM, Farrell M; Brugra T, Bebbington P, Jenkins R and Meltzer H (2004) Prevalence and correlates of self-reported psychotic symptoms in the British Population, British Journal of Psychiatry, 185, 298-305.



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